With a fuel cell, for example, a proton-exchange membrane fuel cell (PEFC), by supplying a fuel gas containing hydrogen and an oxidation gas containing oxygen respectively to two electrodes (an cathode and an anode) facing against each other while sandwiching an electrolytic membrane, performs the reactions shown in the following equation (1) and equation (2), and the chemical energy is directly converted to electrical energy.Cathode reaction: 2H++2e−+(1/2)O2→H2O  (1)Anode reaction: H2→2H++2e−  (2)
As the major structure of the fuel cell, a so-called stack structure is developed. The stack structure of fuel cell has substantially flat shaped membrane electrode assemblies (MEA) and separators that are laminated and joined in the lamination direction.
Here, known as a fuel cell separator is an item having a three layer structure constituted from an anode side plate, a cathode side plate, and an intermediate plate sandwiched between the cathode side plate and the anode side plate. This three layer structure separator includes a reaction gas manifold piercing the three plates, a transfer path provided in the intermediate plate, and long hole shaped through holes provided at the end of the half etched reaction gas flow path at the anode side and cathode side plates. Then, the reaction gas is distributed to the reaction gas flow path via the long hole shaped through holes from the transfer path.
However, with the prior art described above, because the through holes provided on the anode side and cathode side plates are long hole shaped, so when using for a separator for which a reaction gas flow path is not provided in the anode side and cathode side plates (hereafter called a flat separator), there is the risk of the reaction gas supply becoming unstable. Specifically, with the flat separator, because a reaction gas flow path is not provided in the anode side and cathode side plates, these plates can be made thin and flat. In this case, when the strength of the part at which the long hole shaped through holes are formed is insufficient, with deformation, the reaction gas supply becomes unstable, and there was the risk of the fuel cell performance decreasing. Also, because the flat separator does not have the reaction gas flow path in the anode side and cathode side plates, the flat separator cannot control the distribution of the reaction gas by the reaction gas flow path. With the prior art described above, no consideration is made for uniformity of reaction gas distribution when the reaction gas flow path is not provided. Because of this, there was also the risk of the reaction gas distribution becoming uneven, causing a decrease in the fuel cell performance.